This is an application for competitive continuation of our research program, which takes a highly integrative approach to understanding drug abuse by using formal decision models to examine the psychopathology of addictions. In our first project period, we used a single stage decision task (Iowa gambling task) to examine individual differences in how learning, motivational, and choice mechanisms interact in the decision making of drug abusers. In the second project period, we will move beyond the single stage decision approach, to develop and empirically test a computational (formal and mathematical) model for the multi-stage self-control decision problem. Multi-stage decision problems more closely resemble the complex decisions drug users face in which they must make a series of decisions that have both proximal outcomes (i.e., getting high, spending money, relief from withdrawal symptoms) as well as possible long term outcomes (i.e., addiction, social and occupational dysfunction). The model addresses three components: Devaluation of immediate reward and delayed punishment; 2) learning of rewards and punishments from trial by trial experience; and, 3) the critical planning process needed to achieve self control in multiple stage decision scenarios. The project has three specific aims. First, we will determine how regular drug users differ from comparison groups on basic evaluative characteristics, including risk aversion, loss aversion, and temporal discounting. Second, we will examine how these evaluative processes interact with learning to guide behavior over time. Third, we will refine and empirically test our comprehensive model for the multiple stage self-control decision problem in regular drug users. The results of our computational model will be examined in the broader context of drug use, demographic, psychosocial, and personality factors that have been linked to drug abuse. The theoretical model from this work will provide a deeper understanding of individual differences in decision processes of drug abusers, will provide a valuable perspective for the prevention and intervention strategies. [unreadable] [unreadable]